Storage of electrical impulses



Nov. 27, 1951 F. H. BRAY Er AL STORAGE oF ELECTRICAL IMPuLsEs Filed NOV.9, 1946 DESMOND 5. /DLEI? ATTO R N EY Patented Nov. 27, 1951 STORAGE OFELECTRICAL IMPULSES Frederick Harry Bray and Desmond Sydney Ridler,London, England, assgnors to International Standard ElectricCorporation, New

York, N. Y.

Application November 9, 1946, Serial No. 709,027 In Great BritainSeptember 27, 1945 Section 1, Public Law 690, August 8, 1946 Patentexpires September 27, 1965 7 Claims. 1

This invention relates to electrical recording of information.

The object of the invention is to provide a cheap and reliable means ofrecording information.

The main feature of the 'invention consists in recording by means ofthermistors. Another feature consists in the use of thermistor triggercircuits, that is thermistor circuits having two stable current valuesfor an applied voltage.

Thermistors have been in use for some years and are characterised Eby atemperature ccemcient of resistance which may be either positive ornegative and which is moreover many times the corresponding co-eifcientfor a pure metal suitable for a variety of special applica tions inelectric circuits.

Various different materials are available for the resistance element ofa thermistor, these -various materials having diiferent properties inother respect; as one example, a resistance comprises a mixture ofmanganese oxide and nickel oxide, with or without the addition ofcertain other metallic oxides, the mixture being suitably heat treated.

Thermistors have been employed in two different forms (a) known as adirectly heated thermistor and comprising a resistance element of thethermally sensitive resistance material provided with suitable lead-outconductors or terminals, and (b) known as an indirectly heatedthermistor comprising the element (a) provided in addition with aheating coil electrically insulated from the element. A directly heatedthermistor is primarily intended to be controlled by the current whichflows through it and which varies'the temperature and also theresistance accordingly. Such a thermistor will also be affected by thetemperature of its surroundings and may therefore be used forthermostatic control and like purposes with or without direct heating bythe current flowing through it. An indirectly heated thermistor ischiefly designed to be heated by a controlling current which flowsthrough the heating coil and which will usually, but not necessarily, bedifferent from the current which ows through the resistance element, butthis type of thermistor may also be subjectedto either or both of thetypes of control applicable vto a directly heated thermistor.

More detailed information on the properties of thermistors will be foundin an article by G. L. Pearsonin the Bell Laboratories Record, December1940, page 106.

The simplest form of thermistor trigger circuit comprises a seriescombination of thermistor and resistance, but where trigger circuits`are to be used, those described in our co-pending U. S. applicationSerial No. 704,841, now abandoned, are preferred as they are much lesssubject to ambient temperature effects..

The invention will be clearly understood from the following descriptionof a regenerative repeater for selective impulse trains in automatictelephone exchange systems shown in the accompanying drawing. l

The circuit comprises impulse-responsive re lays, a digit-storageuniselector switch RS having two banks of stationary contacts withcooperating movable wipers, rsml and mm2, together with a steppingmagnet RSM .to drive same and a digit-sending switch SS having two banksof stationary contacts with cooperating movable wipers, ssml and ssm2,together with a stepping magnet SSM to drive` same. Thermistor triggercircuits TZ Ta: are individually connected to contact banks rsml andssml, and those circuits connected to bank contacts on which Tsml stopsat the end of the digits received are triggered.

Continuously operating machine impulse springs MCSl, MCS2, control thetransmission of digital impulses over the outgoing line subject to theclosure of the V and IG relays which are under control of switches SS,RS and the triggered thermistor circuits, as will be explained in moredetail below.

Incoming pulses over the incoming line serve alternately to operate therelay A which through the relays B, C serves to operate the steppingmagnet RSM to drive the contacts of this switch RS to the positionindicated by the received dial signals. These dial signals are D. C.pulses and cannot pass to the outgoing line on the output side of therepeater because of the blocking condensers BC and BC shown between thelines. The power driven switch MCSI is continually operated, producingpulses of the same repitition rate as the incoming dialling pulses.However, until relay IG is operated these contacts` are short circuitedand therefore the drive magnet SSM is inoperative until theabove-mentioned operates. The IG relaywill operate for a perioddependent upon the received pulsing signal to step the switch .SSaround. This stepping continues until the movable contact comes to theselected point at which time, through the various circuits as indicated,the IG relay circuit is` interrupted at :c2 so that the stepping willstop. During this period while switch SS is operating, the output loopis completed by closure of contact '04 and removal ofthe short circuitconnections from driven contact MCSZ at b and z'g2. lThis time periodwill coincide with the time period foroperation of magnet SSM so thatcontact MCS2 will open the loop circuit to transmit the same number ofpulses as were received for the dialing. At the termination of thistransmission relay Y is operated again short circuiting contacts MCSZdiscontinuing the transmission of these dialling pulses.

When the circuit is seized, relay A operates, followed by relay B whichbusies the repeater at bl and at b2 prepares the impulsing circuit of animpulse-receiving uniselector switch RS. Line impulses received on relayA step switch RS to a position corresponding to the rst digit received.Slow-release relay C operates in series with magnet RSM, followed by CC.At the end of the impulse train relay C releases and in turn releasesrelay CC. The trigger circuit e. g. Tr associated with the switchposition reached is triggered during the release time of CC by negativebattery applied through the resistance YA. Also during the release ofCC, relay V energises via c3 back,

ce2 front, el back; b front, and locks via '116.

Succeeding digits similarly step switch RS and cause another thermistor-circuit to be triggered.

The triggered circuits are spaced by groups of contacts each equal to astored digit.

On the operation of relay B when the circuit was seized relay W operatedvia g3 back, b3 front, and relay X operated via wl and bl front.

When relay V operatesv at the end of a digit received earth via x2, v3,yi is connected to machine impulse-springs MCSI, and relay IG inparallel.

When the impulse-springs open, relay IG operates, connecting springsMCSI to magnet SSM.

`At the same time contacts g2 remove a shortcircuit from a second pairof machine springs MCSZ; contacts b5, v5 being already opened.

The next closure of the machine springs operate magnet SSM, and the nextopening of the springs steps switch SS and sends an impulse over theoutgoing metallic loop made at '04.

Impulsing continues until wiper ssml reaches a triggered thermistorcircuit. The increase in potential due to the conducting thermistorcauses current to flow in the primary winding of relay TR which is usedas a transformer. The E. M. F. induced in the secondary res a biassedcold cathode tube CCT, and the anode relay Y energises via :cl and 'UIfront. Any suitable electronic tube may be used.

Contacts g4 short-circuit springs MCSZ while contacts yl open thecircuit for SSM and relay IG. Contacts 113 cause relays W, X to releasein turn, providing outgoing interdigital time.

The opening of contacts xl releases relay Y, allowing relays W, X tore-operate and initiate the transmission of the next digit.

Battery through a low resistance YE is con- Ynectedrvia y2 front torestore the triggered thermister circuit to normal condition.

When all the stored digits have been sent in this way, switches SS andRS will be standing on the same trigger circuit position. Relay Zwill,'therefore, operate via c1, ssm2, rsmZ. Contacts 2| release relayV, opening the outgoing impulsing circuits removing the outgoing shortcircuit, and inserting the supervisory relays L and D. Thus, storedinformation denoted by a thermistor circuit whose resistance has beenaltered CIG "the conventional manner.

What is claimed is:

1. An electrical signal recording and repeating circuit comprising anincoming signal line, and outgoing signal line, a plurality ofthermistors, a plurality of individual circuit means respectivelycoupled to each of said thermistors, said means adapted to maintain saidthermistors normally at a predetermined temperature and at a givenresistance value, common circuit means including a source of thermistortriggering potential for 'selectively altering the temperature andresistance value of selected of said thermistors, means coupled to saidincoming line and responsive to signals received thereover forselectively connecting said common circuit means to a selected one ofsaid thermistors thereby to trigger said thermistor, signal transmittingmeans coupled to said outgoing line for transmitting outgoing signalsthereover, switch means having a movable contact and a plurality ofstationary contacts respectively coupled to an associated one of saidthermistors, said movable contact adapted to be moved over saidstationary contacts by said lsignal transmitting means, a normallyinoperative control circuit coupled with said movable contact forcontrolling operation of said signal transmitting means, and meansresponsive to switch connection of said movable contact withy thestationary contact coupled with said selected thermistor for operatingsaid control circuit and for restoring said selected thermistor to saidpredetermined temperature and given resistance value'.

2. An electrical circuit as claimed in claim l, wherein said individualcircuit means comprises a voltage divider network for normallymaintaining a predetermined potential across saidthermistor, and saidcommon circuit means comprises a counter-potential means for alteringsaid first named potential in a predetermined manner.

3. An electrical circuit as claimed in claim l, wherein the means tooperate said control circuit comprises a non-contact making relay.

4. An electrical circuit as claimed in claim 3, wherein said meansfurther comprises a gaseous discharge tube.

5. An electrical signal recording and repeating circuit comprising anincoming signal line, an outgoing signal line, a plurality ofthermistors, a plurality of individual circuit means respectivelycoupled to each of said thermistors, said means adapted to maintain saidthermistors normally at a predetermined temperature and at a givenresistance value, common Vcircuit means including a source of thermistortriggering potential for altering the temperature and resistance valueof selected of said thermistors; a rst switchv means having a pluralityof stationary contacts, a movable contact and means to step said movablecontact over said stationary contacts; means coupling said steppingmeans to said incoming line, said stepping means adapted to step saidmovable contact to a selected stationary contact in response to signalsreceived over said incoming line;

a second switch means having a plurality of stationary contacts, amovable contact and means -to step said movable contact over saidstationary contacts; each of said thermistors respectively connected tocorresponding stationaryA contacts of both said switch means, powerdriven switch means connected to said outgoing line for transmittingsignals thereover, relay means `coupled between said power driven switchmeans and the stepping means of said second switch means, said relaymeans adapted to control stepping of said second switch means by saidpower driven switch means, said relay means under control of the meanscoupling the stepping means of said rst switch means to said incomingline, means coupled to the movable contact of said second switch meansto render ineffective the stepping of the stepping means of said secondswitch by said power driven switch means, said last named means adaptedto become operative when the movable contact of said second switch meansbecomes connected with a stationary contact of said second switch whichis associated with a thermistor whose resistance has been altered bysaid common circuit means, and additional means for restoring atriggered thermistor to said predetermined temperature and givenresistance value, said additional means under control of said means torender ineffective said second switch stepping means.

6. An electrical circuit as claimed in claim 5 wherein additional meansare provided to re-set said output circuit upon the completion of atrain of impulses.

5 to cooperate therewith, said additional movable contacts operating instep with the first mentioned and second mentioned movable contacts, arelay means to energize said relay when said additional movable contactsof said switches are on 10 corresponding contacts.

FREDERICK HARRY BRAY. DESMOND SYDNEY RIDLER.

15 REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS 20 Number Name t Date 1 2,131,589 Halligan Sept.2'?, 193.8l 2,179,826 May Nov. 14, 1939 2,196,173 Black Apr. 9, 19402,236,499 Cesareo Apr. 1, 1941 g5 2,248,212 Albert July 8, 19412,414,488 Shanck Jan. 21, 1947 6 `'1. An electrical circuit as claimedin claim 6, wherein said additional means comprises additional sets ofinterconnected stationary contacts and a pair of additional movablecontacts adapted 1

